Specificity of anti-DNA antibodies in SLE-I. Definition and gross specificity of antibody populations in human SLE plasma.

Populations of anti-DNA antibodies in two SLE plasma were defined based on their patterns of reactivity in inhibition assays with single and double-stranded DNA as well as mono- and oligonucleotides. Two populations of anti-DNA antibodies were seen in both plasma tested. The first population reacted specifically with ssDNA and was inhibited by relatively low concentrations of free nucleotides indicating that it recognized the nucleotide bases in ssDNA. The second population bound both ss and ds calf thymus DNA with apparent equal affinity. The cross-reactive anti-DNA antibodies were inhibited by mononucleotides (at high concentrations) and by single-stranded oligonucleotides (average length tetranucleotides). For one of the plasma tested (PS), pBR322 plasmid DNA (54% G + C) was a significantly more effective inhibitor than calf thymus DNA (39% G + C). These results suggested that nucleotide bases contributed to dsDNA binding by cross-reactive anti-DNA antibodies.